1 #include<cstdlib>
  2 #include<iostream>
  3 #include<cstdio>
  4 #include<cmath>
  5 #include<cstring>
  6 #include <algorithm>
  7 #include<queue>
  8 #include<set>
  9 #define LL long long
 10 #define inf 0x7fffffff
 11 #define E 1e-7
 12 #define M 100
 13 #define N 105
 14 using namespace std;
 15 
 16 
 17 
 18 
 19 int n,m;
 20 double cost[N][N],d[N];
 21 int cap[N][N];
 22 int p[N];
 23 bool inq[N];
 24 int s,t;
 25 int num;
 26 
 27 
 28 double getflow(int s,int t)
 29 {
 30   queue<int> q;
 31   double c=0;
 32   int f=0;
 33   for(;;)
 34     {
 35       for(int i=1;i<=t;i++)
 36       d[i]=inf;
 37       memset(inq,0,sizeof(inq));
 38       d[s]=0.0;
 39       q.push(s);
 40       while(!q.empty())
 41         {
 42           int u=q.front();
 43           q.pop();
 44           inq[u]=0;
 45           for(int i=1; i<=num; i++)
 46             if(cap[u][i]&&d[i]-d[u]-cost[u][i]>-E)
 47               {
 48                 d[i]=d[u]+cost[u][i];
 49                 p[i]=u;
 50                 if(!inq[i])
 51                   {
 52                     q.push(i);
 53                     inq[i]=1;
 54                   }
 55               }
 56         }
 57 
 58 
 59       int a=inf;
 60       for(int i=t; i!=s; i=p[i])
 61         {
 62           a=min(a,cap[p[i]][i]);
 63         }
 64       for(int i=t; i!=s; i=p[i])
 65         {
 66           cap[p[i]][i]-=a;
 67           cap[i][p[i]]+=a;
 68         }
 69       f+=a;
 70       c+=d[t]*(double)a;
 71       if(f==n)
 72       break;
 73     }
 74   return c;
 75 }
 76 int main()
 77 {
 78 #ifndef ONLINE_JUDGE
 79   freopen("ex.in","r",stdin);
 80 #endif
 81   while(scanf("%d%d",&n,&m))
 82     {
 83       if(!n&&!m)
 84         break;
 85         memset(cap,0,sizeof(cap));
 86         memset(cost,0,sizeof(cost));
 87         for(int i=1;i<=n;i++)
 88         for(int j=1;j<=m;j++)
 89         {
 90             scanf("%lf",&cost[i][j+n]);
 91             cost[j+n][i]=-cost[i][j+n];
 92             cap[i][j+n]=1;
 93         }
 94         for(int i=1;i<=n;i++)
 95         cap[0][i]=1;
 96         num=m+n+1;
 97         for(int i=1;i<=m;i++)
 98         cap[i+n][num]=1;
 99         s=0;t=num;
100         double ans=getflow(s,t);
101 //        cout<<"ans="<<ans<<endl;
102         printf("%.2lf\n",ans/n);
103 
104 
105     }
106   return 0;
107 }